Bistable structures for energy absorption I: Metallic structures under tension

Abstract

This paper presents proof-of-concept experiments on metallic bistable structures, and is followed by a companion paper about experiments on composite bistable structures. A bistable structure is characterized by a stress/strain curve with stable branches separated by unstable branches. The authors were interested in a particular bistable structure, one that once activated, has a second stronger state which has the ability to sustain higher loads. This allows for a better distribution of damage. In addition, the structure keeps its integrity for a longer time, leading to a fail safe design. Results on metallic configurations under tensile loading are shown in this paper. In particular, chains with one, two, and three bistable elements of 5052-H32 aluminum were designed, manufactured, tested, and compared to their corresponding baselines. A strain energy increase from 11% to about 30% is shown with respect to the baselines. Moreover, a comparative study with A36 annealed mild steel and C10100 copper shows the effect of the different ductility and stiffness on energy absorption.